PROJECT SUMMARY Widespread human papillomavirus (HPV) vaccination could prevent most HPV-related cancers, which affect over 40,000 people in the United States (US) each year. Despite this potential benefit, HPV vaccine coverage among adolescents remains low. By 2017, fewer than half (39%) of 13-year-olds had completed the 2-dose series. Research to address low coverage suggests that multi-level interventions targeting provider- parent communication and clinical environments may be especially effective. Proven intervention strategies include communication training to improve healthcare providers? HPV vaccine recommendations, as well as assessment and feedback on clinics? HPV vaccine coverage. However, implementing these strategies in real- world clinical settings remains challenging, in part because existing interventions are constrained by their reliance on burdensome group-based meetings. New approaches are needed to deliver the comprehensive training and ongoing data that providers require to adopt and sustain vaccine-related practice improvements. To address this need, the proposed study will enhance and evaluate Up2Date, an existing, theory- informed mobile coaching intervention to improve the delivery of HPV vaccine. Up2Date consists of a brief in- clinic training for healthcare teams, followed by 12 weeks of individualized coaching for providers via a mobile application (app). Specifically, the app supports ongoing assessment and tailored feedback aimed at improving how providers recommend HPV vaccine and address parents? concerns, using a library of research-tested messages. In Aim 1, we will enhance Up2Date to include a dashboard of clinics? HPV vaccine coverage that can be used to set and track shared goals for improvement. In doing so, we will create a multi-level mobile platform to support both provider-level and clinic-level assessment and feedback to improve HPV vaccination. In Aim 2, we will evaluate the feasibility of Up2Date by delivering our intervention to 20 pediatric providers in primary care clinics with HPV vaccine coverage below the national average. We will assess pre/post changes in intermediate outcomes related to clinic-level environments as well as provider-level cognitions and behaviors. We hypothesize that providers? overall recommendation quality will increase between baseline and 12-week follow up. We will also conduct limited efficacy testing of our long-term, family-level outcomes: adolescents? HPV vaccine coverage and parents? satisfaction with care. Finally, we will assess process measures, including the acceptability of and demand for our intervention. These analyses will use qualitative and quantitative data from surveys, interviews, app analytics, and electronic health records. The proposed study builds on the work of a well-established team to evaluate the feasibility of an innovative, multi-level mobile coaching intervention. Results from this feasibility study will generate effect sizes to inform a future randomized controlled trial to test the effectiveness of mobile coaching. If successful, our intervention will improve HPV vaccine coverage and protect adolescents from future HPV-related cancers.